In 3D printing, polymer materials are widely used to create three-dimensional objects. However, some of these polymers are hygroscopic, which means they absorb moisture from their surroundings. This ability to absorb water can have a significant impact on the printing process and the performance of the material itself.

EFFECTS OF MOISTURE IN POLYMERS

The moisture absorbed by polymers can have a significant impact on their behavior during the 3D printing process. Here are some of the negative effects that humidity can cause:

  • RELEASE OF WATER VAPOR, FUMES, AND SOUNDS (WITH VISIBLE SMOKE): When moisture-containing polymer material is extruded at elevated temperatures, water trapped in the material granules can vaporize rapidly, causing water vapor, fumes, and sounds to be released. In some cases, smoke may also be visible, which can affect the quality of the print.
  • MICRO-BUBBLES OR IMPERFECTIONS IN THE PRINT: Trapped moisture can lead to the formation of micro-bubbles in the molten material during extrusion. These microbubbles can cause imperfections in the print, making the surface of the final object less smooth and uniform.
  • INCREASED BURRS IN DISPLACEMENT (STRINGING): Moisture can affect the viscosity of the melt, causing strings of material between different parts of the printed object. This phenomenon is known as "stringing" and is undesirable in 3D printing, as it can require additional post-printing to remove excess strings.
  • EXPANSION OF THE OUTPUT MATERIAL: Trapped moisture can lead to an expansion of the material as it exits the extrusion nozzle. This effect can result in a heavier than expected flow of material, negatively affecting the accuracy of the print.

These issues make the printing process unreliable and result in an uneven surface of the final object.

To determine if the material you are using is sensitive to moisture and how to treat it properly, it is always advisable to contact the manufacturer of the material. This way, you'll be able to adopt the appropriate drying and storage procedures to ensure a high-quality print with your polymer material.

REDUCTION OF MECHANICAL PERFORMANCE

Moisture can also impair the mechanical performance of the polymer material. It can make the material more brittle or less strong, negatively affecting the durability and sturdiness of the printed object. This is especially important if you're printing parts that require some mechanical strength.

HIGH TEMPERATURES

A common problem is the explosion of trapped water. This occurs when the material is brought to high temperatures, often above 200°C.  Water previously absorbed by the polymer can vaporize rapidly, causing warping and imperfections in the print.

DRYING OF POLYMERIC MATERIALS

To mitigate these issues, it is essential to dry hygroscopic polymer materials before printing. This process removes moisture trapped in the material granules, ensuring that the polymer is in optimal condition for printing. It may be necessary to use a vacuum dryer or oven to reach specific temperatures and remove excess moisture.

CHOICE OF MATERIALS

Finally, it's important to note that some polymer materials, such as polypropylene (PP), are non-hygroscopic and do not require drying before printing. In contrast, materials such as PLA and PET-G are notoriously hygroscopic and require special care to ensure high-quality print results.

In summary, moisture is a significant challenge when it comes to 3D printing with hygroscopic polymer materials. Thorough drying of materials is crucial to ensure a reliable printing process and achieve high-quality three-dimensional objects.

However, it is possible to develop processes without dehumidification of the polymer if the part does not require 100% print quality.